1. Field of Invention
This invention relates to a facsimile communication apparatus for allowing a plurality of facsimile machines designed for general telephone networks to communicate with each other via a data communication network, such as a local area network (LAN), and to a program recording unit which stores a program used in the facsimile communication apparatus. This invention also relates to a facsimile communication apparatus for allowing a plurality of facsimile machines to communicate with each other in real time via an Internet Protocol network (referred to as an IP network) based on the IETF (Internet Engineering Task Force), and to a program recording unit storing a program for controlling the facsimile communication apparatus.
2. Description of the Related Art
FIG. 1 illustrates a conventional facsimile communication system using a data communication network, such as an LAN. The transmission side facsimile machine 1 is a G3 facsimile machine designed for general telephone networks, which is categorized according to the T.30 Recommendation standardized by the ITU-T (International Telecommunications Union, Telecommunication Standardization Department). The facsimile machine 1 is connected to the facsimile communication apparatus 10A via a telephone network 2. The facsimile communication apparatus (i.e., the gateway) 10A converts the communication protocol between the telephone network 2 and the LAN 4. The LAN 4 is further connected to another facsimile communication apparatus (i.e., gateway) 10B, to which the receiving side facsimile machine 7 is connected via a telephone network 6. The facsimile machines 1 and 7 have the same standard, and they can mutually transmit and receive image information via the telephone networks. The facsimile communication apparatus 10B has the same structure as the facsimile communication apparatus 10A, and the explanation on it will be omitted.
As shown in FIG. 2, the facsimile communication apparatus 10A has a terminal accommodation circuit 3a, to which a plurality of facsimile machines 1a through 1n are connected via the corresponding telephone lines 2a, 2b, . . . , 2n of the telephone network 2. The terminal accommodation circuit 3a is connected to a switch circuit 3b which selects the line which is currently requesting a facsimile transmission from among the telephone lines 2a through 2n. A CODEC 3c is connected to the switch circuit 3b in order to terminate the selected line. The CODEC 3c is a encoder/decoder which converts analog signals received from the telephone line 2a into digital signals, and which decodes digital signals into analog signals in order to output data to the telephone line 2a.
The terminal accommodation circuit 3a, the switch circuit 3b and the CODEC 3c are connected to the CPU 3e via a common bus 3d. The CPU 3e controls the overall operations of the facsimile communication apparatus 10A. A memory 3f and a LAN control circuit 3g are also connected to the common bus 3d. The memory 3f temporarily stores digitized information prior to transmitting the digitized information. The LAN control circuit 3g performs data transfer in a packet format to and from another facsimile communication apparatus 10B via the LAN 4.
The facsimile machine 1 of FIG. 1 is connected to the facsimile machine 7 via the telephone line 2, the facsimile communication apparatus 10A, the LAN 4, the facsimile communication apparatus 10B, and the telephone line 6, in that order. If pixel information is transmitted from the facsimile machine 1a of FIG. 2 to the facsimile machine 7, the pixel data read by the facsimile machine 1a from the original document is encoded according to a prescribed coding rule. The encoded pixel data is modulated by, for example, a 9600 bps MODEM installed in the facsimile machine 1a to produce an analog signal in the voice frequency band. The analog signal is transmitted to the facsimile communication apparatus 10A through the telephone line 2a. The CODEC 3c of the facsimile communication apparatus 10A samples the analog signal supplied via the telephone line 2a based on a sampling signal of, for example, 8 KHz, and converts the sampled analog signal into an 8-bit digital signal for each sampling.
Thus, the analog signal is converted into a 64 Kbps digital signal by the CODEC 3c, which is then read by the CPU 3e via the common bus 3d. The CPU 3e edits the digital signal into a packet data of a predetermined size, and temporarily stores the packet data in the memory 3f. The packet data stored in the memory 3f is read out by the LAN control circuit 3g, and transmitted to the receiving side facsimile communication apparatus 10B via the LAN 4. In the facsimile communication apparatus 10B, the packet data received from the LAN control circuit 3g is temporarily stored in a memory. Then, the stored data is read out by a CPU corresponding to the CPU 3e, and supplied to a CODEC corresponding to the CODEC 3c, which converts the data into an analog signal and outputs the analog signal to the facsimile machine 7 via the telephone network 6. Thus, the analog signal transmitted from the facsimile machine 1a is converted into a digital signal by the CODEC 3c of the facsimile communication apparatus 10A, and transferred as a packet data to the receiving side facsimile communication apparatus 10B via the LAN 4.
However, the conventional facsimile communication system has several problems.
Because the transfer path of the LAN 4 is divided into a plurality of channels in order to transfer the data in a packet format, the transfer delay time of the packet data is not constant. In addition, if the traffic of the LAN 4 is heavy, the packet data may be lost half way through the transmission path. For these reasons, the analog signals which are being decoded by the CODEC 3c of the receiving side facsimile communication apparatus 10B may sometimes be interrupted and, as a result, wrong data is received by the receiving side facsimile machine 7.
Furthermore, although the inherent data transfer rate between the facsimiles machines 1a and 7 is, for example, 9600 bps, the data is transferred at 64 Kbps in the LAN 4, which is inefficient from the standpoint of data transfer capacity.